U.S. patent application number 16/611879 was filed with the patent office on 2021-06-03 for production method for hexafluoro-1,3-butadiene.
This patent application is currently assigned to SHOWA DENKO K.K.. The applicant listed for this patent is SHOWA DENKO K.K.. Invention is credited to Yohsuke FUKUCHI, Mitsuhiro HINO, Nozomi INOUE, Atsushi NAKAMURA, Tomoki SEKIGUCHI.
Application Number | 20210163382 16/611879 |
Document ID | / |
Family ID | 1000005419436 |
Filed Date | 2021-06-03 |
United States Patent
Application |
20210163382 |
Kind Code |
A1 |
FUKUCHI; Yohsuke ; et
al. |
June 3, 2021 |
PRODUCTION METHOD FOR HEXAFLUORO-1,3-BUTADIENE
Abstract
Provided is a method that is for producing
hexafluoro-1,3-butadiene, discharges small amounts of industrial
wastes, and is industrially applicable. The method for producing
hexafluoro-1,3-butadiene includes a reaction step of reacting a
halogenated butane represented by chemical formula,
CF.sub.2X.sup.1-CFX.sup.2-CFX.sup.3-CF.sub.2X.sup.4 (X.sup.1,
X.sup.2, X.sup.3, and X.sup.4 are each independently a halogen atom
other than a fluorine atom) in an organic solvent in the presence
of zinc to eliminate the halogen atoms, X.sup.1, X.sup.2, X.sup.3,
and X.sup.4, other than the fluorine atoms to generate
hexafluoro-1,3-butadiene, giving a reaction product containing the
hexafluoro-1,3-butadiene, and an aftertreatment step of separating
the hexafluoro-1,3-butadiene from the reaction product produced in
the reaction step, then adding water to a reaction product residue
after the separating, and removing the organic solvent, giving an
aqueous solution of zinc halide.
Inventors: |
FUKUCHI; Yohsuke; (Tokyo,
JP) ; NAKAMURA; Atsushi; (Tokyo, JP) ; INOUE;
Nozomi; (Tokyo, JP) ; HINO; Mitsuhiro; (Tokyo,
JP) ; SEKIGUCHI; Tomoki; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHOWA DENKO K.K. |
Tokyo |
|
JP |
|
|
Assignee: |
SHOWA DENKO K.K.
Tokyo
JP
|
Family ID: |
1000005419436 |
Appl. No.: |
16/611879 |
Filed: |
April 25, 2018 |
PCT Filed: |
April 25, 2018 |
PCT NO: |
PCT/JP2018/016881 |
371 Date: |
November 8, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 17/23 20130101;
C07C 17/383 20130101 |
International
Class: |
C07C 17/23 20060101
C07C017/23; C07C 17/383 20060101 C07C017/383 |
Foreign Application Data
Date |
Code |
Application Number |
May 22, 2017 |
JP |
2017-101063 |
Claims
1. A method for producing hexafluoro-1,3-butadiene, the method
comprising: a reaction step of reacting a halogenated butane
represented by chemical formula,
CF.sub.2X.sup.1-CFX.sup.2-CFX.sup.3-CF.sub.2X.sup.4 (X.sup.1,
X.sup.2, X.sup.3, and X.sup.4 are each independently a halogen atom
other than a fluorine atom) in an organic solvent in the presence
of zinc to eliminate the halogen atoms, X.sup.1, X.sup.2, X.sup.3,
and X.sup.4, other than the fluorine atoms to generate
hexafluoro-1,3-butadiene, giving a reaction product containing the
hexafluoro-1,3-butadiene; and an aftertreatment step of separating
the hexafluoro-1,3-butadiene from the reaction product produced in
the reaction step, then adding water to a reaction product residue
after the separating, and removing the organic solvent, giving an
aqueous solution of zinc halide.
2. The method for producing hexafluoro-1,3-butadiene according to
claim 1, wherein the organic solvent is an alcohol.
3. The method for producing hexafluoro-1,3-butadiene according to
claim 2, wherein the alcohol is at least one of methanol, ethanol,
1-propanol, and 2-propanol.
4. The method for producing hexafluoro-1,3-butadiene according to
claim 1, further comprising a neutralization step of bringing the
hexafluoro-1,3-butadiene separated from the reaction product
produced in the reaction step into contact with an alkali, and a
water removal step of removing water from the
hexafluoro-1,3-butadiene that has been brought into contact with
the alkali in the neutralization step.
5. The method for producing hexafluoro-1,3-butadiene according to
claim 4, further comprising a purification step of distilling the
hexafluoro-1,3-butadiene from which water has been removed in the
water removal step, by using at least two distillation columns to
purify the hexafluoro-1,3-butadiene.
6. The method for producing hexafluoro-1,3-butadiene according to
claim 1, wherein in the aftertreatment step, a hydrogen halide is
added together with the water to the reaction product residue.
7. The method for producing hexafluoro-1,3-butadiene according to
claim 2, further comprising a neutralization step of bringing the
hexafluoro-1,3-butadiene separated from the reaction product
produced in the reaction step into contact with an alkali, and a
water removal step of removing water from the
hexafluoro-1,3-butadiene that has been brought into contact with
the alkali in the neutralization step.
8. The method for producing hexafluoro-1,3-butadiene according to
claim 3, further comprising a neutralization step of bringing the
hexafluoro-1,3-butadiene separated from the reaction product
produced in the reaction step into contact with an alkali, and a
water removal step of removing water from the
hexafluoro-1,3-butadiene that has been brought into contact with
the alkali in the neutralization step.
9. The method for producing hexafluoro-1,3-butadiene according to
claim 2, wherein in the aftertreatment step, a hydrogen halide is
added together with the water to the reaction product residue.
10. The method for producing hexafluoro-1,3-butadiene according to
claim 3, wherein in the aftertreatment step, a hydrogen halide is
added together with the water to the reaction product residue.
11. The method for producing hexafluoro-1,3-butadiene according to
claim 4, wherein in the aftertreatment step, a hydrogen halide is
added together with the water to the reaction product residue.
12. The method for producing hexafluoro-1,3-butadiene according to
claim 5, wherein in the aftertreatment step, a hydrogen halide is
added together with the water to the reaction product residue.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for producing
hexafluoro-1,3-butadiene.
BACKGROUND ART
[0002] Hexafluoro-1,3-butadiene is useful, for example, as an
etching gas for semiconductors. As the production method for
hexafluoro-1,3-butadiene, various methods have been known. For
example, PTL 1 discloses a method of subjecting
1,2,3,4-tetrachlorohexafluorobutane to dechlorination reaction in
dioxane in the presence of magnesium at -78.degree. C. PTL 2
discloses a method of subjecting
1,2,3,4-tetrachlorohexafluorobutane to dechlorination reaction in
2-propanol in the presence of zinc.
CITATION LIST
Patent Literatures
[0003] PTL 1: WO 2005/23734
[0004] PTL 2: JP 5005681 B
SUMMARY OF INVENTION
Technical Problem
[0005] The methods disclosed in PTLs 1 and 2, however, have a
problem that, after the reaction, a large amount of a mixture of an
organic solvent (dioxane, 2-propanol), a metal salt (magnesium
chloride, zinc chloride), and an unreacted compound is formed,
resulting in industrial wastes. Hence, the methods disclosed in
PTLs 1 and 2 are unsuitable for industrial production methods for
hexafluoro-1,3-butadiene. The present invention is intended to
provide a method that is for producing hexafluoro-1,3-butadiene,
discharges small amounts of industrial wastes, and is industrially
applicable.
Solution to Problem
[0006] To solve the problems, aspects of the present invention are
the following [1] to [6].
[0007] [1] A method for producing hexafluoro-1,3-butadiene
includes
[0008] a reaction step of reacting a halogenated butane represented
by chemical formula,
CF.sub.2X.sup.1-CFX.sup.2-CFX.sup.3-CF.sub.2X.sup.4 (X.sup.1,
X.sup.2, X.sup.3, and X.sup.4 are each independently a halogen atom
other than a fluorine atom) in an organic solvent in the presence
of zinc to eliminate the halogen atoms, X.sup.1, X.sup.2, X.sup.3,
and X.sup.3, other than the fluorine atoms to generate
hexafluoro-1,3-butadiene, giving a reaction product containing the
hexafluoro-1,3-butadiene, and
[0009] an aftertreatment step of separating the
hexafluoro-1,3-butadiene from the reaction product produced in the
reaction step, then adding water to a reaction product residue
after the separating, and removing the organic solvent, giving an
aqueous solution of zinc halide.
[0010] [2] In the method for producing hexafluoro-1,3-butadiene
according to the aspect [1], the organic solvent is an alcohol.
[0011] [3] In the method for producing hexafluoro-1,3-butadiene
according to the aspect [2], the alcohol is at least one of
methanol, ethanol, 1-propanol, and 2-propanol.
[0012] [4] The method for producing hexafluoro-3,3-butadiene
according to any one of the aspects [1] to [3] further includes a
neutralization step of bringing the hexafluoro-1,3-butadiene
separated from the reaction product produced in the reaction step
into contact with an alkali, and a water removal step of removing
water from the hexafluoro-1,3-butadiene that has been brought into
contact with the alkali in the neutralization step.
[0013] [5] The method for producing hexafluoro-1,3-butadiene
according to the aspect [4] further includes a purification step of
distilling the hexafluoro-1,3-butadiene from which water has been
removed in the water removal step, by using at least two
distillation columns to purify the hexafluoro-1,3-butadiene.
[0014] [6] In the method for producing hexafluoro-1,3-butadiene
according to any one of the aspects [1] to [5], in the
aftertreatment step, a hydrogen halide is added together with the
water to the reaction product residue.
Advantageous Effects of Invention
[0015] The method for producing hexafluoro-1,3-butadiene according
to the present invention discharges small amounts of industrial
wastes and is industrially applicable.
DESCRIPTION OF EMBODIMENTS
[0016] An embodiment of the present invention will now be
described. The present embodiment is merely an example of the
present invention, and the present invention is not limited to the
present embodiment. Various modifications or improvements can be
made in the present embodiment, and such various modifications and
improvements can be encompassed by the present invention.
[0017] A method for producing hexafluoro-1,3-butadiene of the
embodiment includes a reaction step of reacting a halogenated
butane represented by chemical formula,
CF.sub.2X.sup.1-CFX.sup.2-CFX.sup.3-CF.sub.2X.sup.4 (X.sup.1,
X.sup.2, X.sup.3, and X.sup.4 are each independently a halogen atom
other than a fluorine atom) in an organic solvent in the presence
of zinc to eliminate the halogen atoms, X.sup.1, X.sup.2, X.sup.3,
and X.sup.4, other than the fluorine atoms to generate
hexafluoro-1,3-butadiene, giving a reaction product containing
hexafluoro-1,3-butadiene, and an aftertreatment step of separating
the hexafluoro-1,3-butadiene from the reaction product produced in
the reaction step, then adding water to a reaction product residue
after the separating, and removing the organic solvent, giving an
aqueous solution of zinc halide.
[0018] By such a method for producing hexafluoro-1,3-butadiene of
the embodiment, an organic solvent and a zinc halide can be
recovered in the aftertreatment step, and thus the method
discharges small amounts of industrial wastes and is industrially
applicable. In addition, an industrially valuable, highly pure,
aqueous solution of zinc halide can be obtained. Moreover,
hexafluoro-1,3-butadiene can be produced safely and inexpensively.
In the present invention, "hexafluoro-1,3-butadiene" means
"1,1,2,3,4,4-hexafluoro-1,3-butadiene".
[0019] Hereinafter, the method for producing
hexafluoro-1,3-butadiene of the embodiment will be described in
further detail. First, the reaction step will be described.
Reaction Step
[0020] The halogenated butane represented by chemical formula,
CF.sub.2X.sup.1-CFX.sup.2-CFX.sup.3-CF.sub.2X.sup.4, may be any
type, and X.sup.1, X.sup.2, X.sup.3, and X.sup.4 are each
independently a halogen atom other than a fluorine atom and may be
any of chlorine, bromine, and iodine. All of X.sup.1, X.sup.2,
X.sup.3, and X.sup.4 may be the same halogen atom, or some may be
the same, and the others may be different halogen atoms. For
example, 1,2,3,4-tetrachlorohexafluorobutane in which X.sup.1,
X.sup.2, X.sup.3, and X.sup.4 are each chlorine can be used as the
halogenated butane. In the present invention,
"1,2,3,4-tetrachlorohexafluorobutane" means
"1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane".
[0021] The organic solvent used in the reaction step may be any
type that does not interfere with the progress of dehalogenation
reaction that eliminates halogen atoms other than a fluorine atom
from a halogenated butane to give hexafluoro-1,3-butadiene. For
example, an alcohol, acyclic ether, an aromatic hydrocarbon, an
amide solvent, an organic acid, or a mixed solvent of them can be
used.
[0022] Examples of the cyclic ether include tetrahydrofuran and
dioxane. Examples of the aromatic hydrocarbon include benzene and
toluene. Examples of the amide solvent include
N,N-dimethylformamide. Examples of the organic acid include acetic
acid. Of these organic solvents, an alcohol appropriately helps the
dehalogenation reaction to proceed and is preferred in the after
treatment step as described later. The alcohol may be any type,
and, for example, at least one of methanol, ethanol, 1-propanol,
and 2-propanol can be used.
[0023] In the reaction step, the mass ratio of the zinc used to the
organic solvent used ([amount of zinc]/[amount of organic solvent])
may be in a range of 0.2 or snore and 2.0 or less.
[0024] The shape of the zinc is not specifically limited as long as
the dehalogenation reaction proceeds, but is preferably in a powder
form or a ribbon form, and is more preferably in a powder form from
the viewpoint of reactivity or handling properties. A powder zinc
preferably has an average particle diameter of 0.04 mm or more and
10.0 mm or less.
[0025] In the reaction step, for example, zinc and an organic
solvent can be mixed, and a halogenated butane can be gradually
added typically at a temperature of 20.degree. C. or more and
150.degree. C. or less, preferably 30.degree. C. or more and
95.degree. C. or less, while the pressure is typically maintained
at 0.05 MPa or more and 1 MPa or less. This operation enables the
dehalogenation reaction of eliminating halogen atoms other than a
fluorine atom from the halogenated butane to generate
hexafluoro-1,3-butadiene.
[0026] The mass ratio of the halogenated butane used to the zinc
used ([amount of halogenated butane]/[amount of zinc]) may be in a
range of 1 or more and 12 or less.
[0027] The reaction product containing hexafluoro-1,3-butadiene
produced in the reaction step may be introduced, for example, to a
distillation column, and the hexafluoro-1,3-butadiene may be
gasified in the distillation column to separate a liquid phase
mainly containing an organic solvent from a gas phase mainly
containing the hexafluoro-1,3-butadiene. The liquid phase contains
an unreacted material and by-products together with the organic
solvent.
Neutralization Step
[0028] In the method for producing hexafluoro-1,3-butadiene of the
embodiment, in order to remove hydrogen fluoride as a by-product
contained in the hexafluoro-1,3-butadiene separated from the
reaction product, the hexafluoro-1,3-butadiene separated from the
reaction product may be brought into contact with an alkali to be
neutralized (neutralization step). The neutralization stop is
preferably performed as follows: for example, the reaction product
is introduced to a distillation column to separate the
hexafluoro-1,3-butadiene as a gas phase; and then the separated gas
phase is brought into contact with an alkali. The neutralization
step is preferably performed in a temperature condition of
-15.degree. C. or more and 60.degree. C. or less.
[0029] The alkali may be any type, and examples include aqueous
alkali solutions such as an aqueous sodium hydroxide solution and
an aqueous potassium hydroxide solution. Alternatively, a solid
alkali may be used. Examples of the solid alkali include refining
agents containing an alkali compound such as an alkali metal
compound and an alkaline earth metal compound and a support such as
a carbonaceous solid material, alumina, and zeolite and a commonly
used soda lime. The separated gas phase can be brought into contact
with the alkali, for example, by gas bubbling of the gas phase in
the aqueous alkali solution.
Water Removal Step
[0030] In the method for producing hexafluoro-1,3-butadiene of the
embodiment, the hexafluoro-1,3-butadiene that has been brought into
contact with the alkali in the neutralization step may be subjected
to a water removal treatment (water removal step). The
hexafluoro-1,3-butadiene after the neutralization step contains
water, and thus the water removal step is preferably performed
subsequent to the neutralization step to remove water from the
hexafluoro-1,3-butadiene. The hexafluoro-1,3-butadiene that has
been brought into contact with the alkali in the neutralization
step may contain intermediates of the dehalogenation reaction in
addition to the water.
[0031] The water removal method is not specifically limited, and a
water removal treatment by contact with zeolite may be performed.
Specific examples of the zeolite include molecular sieves 3A, 4A,
and 5A. The water removal treatment is preferably performed in a
temperature condition of -15.degree. C. or more and 60.degree. C.
or less. The water removal treatment may be performed in a gas
state or a liquid state but is preferably performed in a liquid
state. The water removal step is preferably performed in a
switching system including two or more lines.
Purification Step
[0032] The method for producing hexafluoro-1,3-butadiene of the
embodiment may further include a purification step of distilling
the hexafluoro-1,3-butadiene from which water has been removed in
the water removal stop, by using at least two distillation columns
to purify the hexafluoro-1,3-butadiene. The
hexafluoro-1,3-butadiene from which water has been removed in the
water removal step can contain an unreacted halogenated butane or
intermediates of the dehalogenation reaction.
[0033] In an example of the purification step, first, the
hexafluoro-1,3-butadiene from which water has been removed in the
water removal step is introduced to a first distillation column,
for example, by using a pump or a compressor. From the first
distillation column, low-boiling components (for example, air,
carbon monoxide, carbon dioxide) are extracted as the overhead
distillate. As the bottom distillate, hexafluoro-1,3-butadiene is
mainly extracted and is introduced to a second distillation
column.
[0034] Next, from the second distillation column, a purified
hexafluoro-1,3-butadiene, the target compound, is extracted as the
overhead distillate and is collected as a product. Meanwhile, as
the bottom distillate of the second distillation column,
high-boiling components (for example, a small amount of an organic
solvent, intermediates of the dehalogenation reaction) are
extracted. At least a part of the high-boiling components may be
returned to the reaction step.
[0035] In another example of the purification step, first, the
hexafluoro-1,3-butadiene from which water has been removed in the
water removal step is introduced to a first distillation column.
From the first distillation column, low-boiling components and
hexafluoro-1,3-butadiene are extracted as the overhead distillate.
As the bottom distillate, the high-boiling components described
above are extracted. At least a part of the high-boiling components
may be returned to the reaction stop.
[0036] Next, the mixture of the low-boiling components and the
hexafluoro-1,3-butadiene extracted from the head of the first
distillation column is introduced to a second distillation column.
From the second distillation column, the low-boiling components
(for example, air, carbon monoxide, carbon dioxide) are extracted
as the overhead distillate. Meanwhile, as the bottom distillate
from the second distillation column, a purified
hexafluoro-1,3-butadiene, the target compound, is extracted and is
collected as a product.
Aftertreatment Step
[0037] Next, the aftertreatment step will be described. The
aftertreatment step is a step of separating the
hexafluoro-1,3-butadiene from the reaction product produced in the
reaction step, then adding water to a reaction product residue
after the separating, and removing the organic solvent to give an
aqueous solution of zinc halide. The reaction product residue after
the separation of the hexafluoro-1,3-butadiene may be introduced,
for example, to a metal reaction container coated with Teflon
(registered trademark), and water may be added.
[0038] The mass ratio of the reaction product residue to the water
([amount of reaction product residue]/[amount of water]) may be in
a range of 0.5 or more and 2.0 or less. As the water, tap water,
ion-exchanged water, distilled water, pure water, ultrapure water,
or the like can be used, and pure water or ultrapure water is
preferred.
[0039] In the aftertreatment step, an inorganic acid such as a
hydrogen halide may be added together with water, as needed. A
hydrogen halide reacts with unreacted zinc to convert the zinc into
a zinc ion and thus improves the yield of a zinc halide. Examples
of the hydrogen halide include hydrogen fluoride, hydrogen
chloride, hydrogen bromide, and hydrogen iodide. For example, in
order to give an aqueous zinc chloride solution in the
aftertreatment step, hydrochloric acid is suitably added as the
inorganic acid. The concentration of hydrochloric acid is not
specifically limited and is preferably 1.0% by mass or more and
37.0% by mass or less.
[0040] When a solution obtained by addition of water to the
reaction product residue in the aftertreatment step contains solid
substances, solid-liquid separation may be performed. The
solid-liquid separation may be performed by any method, which can
be selected from settling/floating, filtration, centrifugation, and
the like. Of the above methods, filtration is a simple method and
thus is suitably used.
[0041] Next, from the solution after solid-liquid separation, the
organic solvent is removed. The organic solvent may be removed by
any method, and distillation is preferred. The distillation may be
any type, which can be selected from atmospheric distillation,
vacuum distillation, molecular distillation, and the like. As the
atmospheric distillation, a known method including simple
distillation and distillation using a distillation column with
trays, such as an Oldershaw column, can be used. As the vacuum
distillation, typical vacuum distillation and vacuum distillation
using a rotary evaporator can be used.
[0042] In order to efficiently remove the organic solvent from the
solution obtained by addition of water to the reaction product
residue in the aftertreatment step, the organic solvent is
preferably an alcohol, more preferably at least one of methanol,
ethanol, 1-propanol, and 2-propanol, and even more preferably
2-propanol. These alcohols can be simply removed by distillation
from the solution obtained by addition of water to the reaction
product residue in the aftertreatment step.
[0043] By collecting the residue after removal of the organic
solvent, an aqueous solution of zinc halide can be recovered as a
product. The aqueous solution of zinc halide has high purity and is
industrially valuable. When a resulting aqueous solution of zinc
halide is colored, the aqueous solution of zinc halide may be
brought into contact with a refining agent to remove the color.
Examples of the refining agent include carbonaceous solid materials
typified by activated carbon, zeolite, activated alumina, and
silica gel, and activated carbon is preferred.
EXAMPLES
[0044] The present invention will next be described in further
detail with reference to examples and comparative examples.
Example 1
Reaction step
[0045] In an SUS316 autoclave having an internal volume of 500 ml,
119 g of 2-propanol as an organic solvent and 82.4 g of granular
metal zinc were placed. The autoclave had a jacket with a cooling
structure and a stirrer at the upper part, and the heating system
was a jacket heating system.
[0046] While the content in the autoclave was stirred, the
temperature was increased to 70.degree. C. While the content in the
autoclave was maintained at a temperature of 70.degree. C. under
normal pressure, 149 g of 1,2,3,4-tetrachlorohexafluorobutane was
added dropwise at a drop rate of 9.31 g per hour and was reacted
for 5 hours. After completion of the reaction for 5 hours, the
reaction product was further heated to vaporize a part of the
organic solvent (2-propanol) and the product, and the vapor of them
was cooled, liquified, and collected. The obtained liquid was
subjected to simple distillation (first distillation system), and a
gas phase mainly containing the product was separated from a liquid
phase mainly containing the organic solvent. The separated product
was analyzed by gas chromatography to show 94.5% by volume of
hexafluoro-1,3-butadiene and 5.5% by volume of other
components.
Water Removal Step, Purification Step
[0047] Through a neutralization step in the condition of bubbling
in an aqueous potassium hydroxide solution, the product was
subjected to a water removal treatment with molecular sieves in a
temperature condition of 0.degree. C., then high-boiling components
and low-boiling components were removed by using two distillation
columns (second distillation system), and a purified
hexafluoro-1,3-butadiene (hereinafter called "purified product 1")
was obtained. The purified product 3 was analyzed by gas
chromatography to show that the hexafluoro-1,3-butadiene had a
purity of 99.995% by volume or more. Low-boiling components were
further removed by using another distillation column (third
distillation system) to give a purified hexafluoro-1,3-butadiene
(hereinafter called "purified product 2"). The purified product 2
was analyzed by gas chromatography to show that the
hexafluoro-1,3-butadiene had a purity of 99.999% by volume or
more.
Aftertreatment Step (Addition)
[0048] To 150 g of the reaction product residue obtained in the
reaction step (the reaction product residue after separation by
further heating to vaporize a part of the organic solvent and the
product), 150 g of water and 2.5 g of 35% by mass hydrochloric acid
were added, and the whole was stirred. The mixture was then
filtered through a filter paper, type 5B, for quantitative analysis
to remove insoluble substances, giving a filtrate.
After Treatment Step (Formation of Aqueous Zinc Chloride
Solution)
[0049] The filtrate obtained in the aftertreatment step (addition)
was subjected to simple distillation (fourth distillation system)
to remove the organic solvent (2-propanol) by evaporation.
Distillation was performed until the distillate fraction containing
2-propanol reached a total amount of 150 g, and then the
distillation residue was collected to give an aqueous zinc chloride
solution having a zinc chloride concentration of 51% by mass. The
aqueous zinc chloride solution had a sufficiently, industrially
valuable purity, which was shown by the following purity
determination results.
Determination of Purity
[0050] The purity of the aqueous zinc chloride solution was
determined by the following two methods.
Determination 2
[0051] The zinc in the aqueous zinc chloride solution was
quantitatively determined by chelatometric titration using
ethylenediaminetetraacetic acid (EDTA), and the result was
converted into a zinc chloride amount. In the measurement, all zinc
in the aqueous zinc chloride solution was assumed to be in the form
of zinc chloride.
[0052] Next, the water in the aqueous zinc chloride solution was
quantitatively determined by Karl Fischer method. The amount of the
zinc chloride and the amount of the water were subtracted from the
total amount of the aqueous zinc chloride solution to give the
impurity amount in the aqueous zinc chloride solution. As a result,
the impurity amount in the aqueous zinc chloride solution was less
than the detection limit.
Determination 2
[0053] The aqueous zinc chloride solution was analyzed by gas
chromatography. Only 832 ppm by mass of 2-propanol was
quantitatively determined as the component other than zinc chloride
or water. Diisopropyl ether and freons were detected as other
impurities, but these amounts were too small for quantitative
determination.
Example 2
Reaction Step
[0054] The step was the same as in Example 1.
Aftertreatment Step (Addition)
[0055] The step was the same as in Example 1.
Aftertreatment Step (Formation of Aqueous Zinc Chloride
Solution)
[0056] The filtrate obtained in the aftertreatment step (addition)
was distilled with a rotary evaporator to remove the organic
solvent (2-propanol) by evaporation. Distillation was performed
until the distillate fraction containing 2-propanol reached a total
amount of 150 g, and then the distillation residue was collected to
give an aqueous zinc chloride solution having a zinc chloride
concentration of 48% by mass. The aqueous zinc chloride solution
had a sufficiently, industrially valuable purity, which was shown
by the following purity determination results.
Determination of Purity
[0057] The purity of the aqueous zinc chloride solution was
determined in the same manner as in Example 1.
Determination 1
[0058] The impurity amount in the aqueous zinc chloride solution
was less than the detection limit.
Determination 2
[0059] Only 1,002 ppm by mass of 2-propanol was quantitatively
determined as the component other than zinc chloride or water.
Diisopropyl ether and freons were detected as other impurities, but
these amounts were too small for quantitative determination.
Example 3
Reaction Step
[0060] The step was the same as in Example 1.
Aftertreatment Step (Addition)
[0061] To 500 g of the reaction product residue obtained in the
reaction step (the reaction product residue after separation by
further heating to vaporize a part of the organic solvent and the
product), 500 g of water and 1.0 g of 35% by mass hydrochloric acid
were added, and the whole was stirred. The mixture was then
filtered through a filter paper, type 5B, for quantitative analysis
to remove insoluble substances, giving a filtrate.
Aftertreatment Step (Formation of Aqueous Zinc Chloride
Solution)
[0062] The filtrate obtained in the aftertreatment step (addition)
was distilled at a reflux ratio of 5:1 by using an Oldershaw type
distillation apparatus having five trays to remove the organic
solvent (2-propanol) by evaporation. Distillation was performed
until the distillate fraction containing 2-propanol reached a total
amount of 500 g, and then the distillation residue was collected to
give an aqueous zinc chloride solution having a zinc chloride
concentration of 49% by mass. The aqueous zinc chloride solution
had a sufficiently, industrially valuable purity, which was shown
by the following purity determination results.
Determination of Purity
[0063] The purity of the aqueous zinc chloride solution was
determined in the same manner as in Example 1.
Determination 1
[0064] The impurity amount in the aqueous zinc chloride solution
was less than the detection limit.
Determination 2
[0065] Only 486 ppm by mass of 2-propanol was quantitatively
determined as the component other than zinc chloride or water.
Diisopropyl ether and freons were detected as other impurities, but
these amounts were too small for quantitative determination.
Comparative Example 1
Reaction step
[0066] The step was the same as in Example 1.
Aftertreatment Step (Without Addition)
[0067] Through a filter paper, type 5B, for quantitative analysis,
150 g of the reaction product residue obtained in the reaction step
(the reaction product residue after separation by further heating
to vaporize a part of the organic solvent and the product) was
filtered to remove insoluble substances, giving a filtrate.
Aftertreatment Step (Formation of Aqueous Zinc Chloride
Solution)
[0068] The filtrate obtained in the aftertreatment step (without
addition) was heated to evaporate the organic solvent (2-propanol),
then solid substances were removed, and 75 g of water was added,
giving an aqueous zinc chloride solution having a zinc chloride
concentration of 45% by mass. The obtained aqueous zinc chloride
solution contained large amounts of impurities and had a low
industrial value, which was shown by the following purity
determination results.
Determination of Purity
[0069] The purity of the aqueous zinc chloride solution was
determined in the same manner as in Example 1.
Determination 1
[0070] The impurity amount in the aqueous zinc chloride solution
was 5% by mass.
Comparative Example 2
Reaction Step
[0071] The step was the same as in Example 1.
Aftertreatment Step (Formation of Aqueous Zinc Chloride Solution
Without Addition or Filtration)
[0072] First, 150 g of the reaction product residue obtained in the
reaction step (the reaction product residue after separation by
further heating to vaporize a part of the organic solvent and the
product) was heated to evaporate the organic solvent (2-propanol),
then solid substances were removed, and 75 g of water was added,
giving an aqueous zinc chloride solution having a zinc chloride
concentration of 45% by mass. The obtained aqueous zinc chloride
solution contained large amounts of impurities and had a low
industrial value, which was shown by the following purity
determination results.
Determination of Purity
[0073] The purity of the aqueous zinc chloride solution was
determined in the same manner as in Example 1.
Determination 1
[0074] The impurity amount in the aqueous zinc chloride solution
was 5% by mass.
* * * * *